Open AccessHistological evidence for reversible cardiomyocyte changes and serum cardiac troponin T elevation after exercise in rats
Author(s) -
Nie Jinlei,
George Keith,
Duan Fei,
Tong Tomas K.,
Tian Ye
Publication year - 2016
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.13083
Subject(s) - troponin complex , saline , medicine , troponin t , troponin , endocrinology , myocardial infarction
This study characterized cardiac troponin T ( cTnT ) appearance and associated histological evidence of reversible or irreversible changes in myocardial ultrastructure, determined via electron microscopy, in rats undertaking isoproterenol ( ISO ) infusion or an endurance exercise challenge. Male rats were randomized into ISO and exercise groups. In ISO trials rats were killed 5 h ( ISO ‐5H) and 24 h ( ISO ‐ REC 19H) after a single ISO or saline injection ( SAL ‐5H; SAL ‐ REC 19H). In the exercise trials rats were killed before, as a control ( EXE ‐ CON ), immediately after ( EXE ‐ END 5H) and 19 h after ( EXE ‐ REC 19H) a 5‐h bout of swimming with 5% body weight attached to their tail. Serum cTnT was quantified by electrochemiluminescence, and myocardial samples in ISO ‐ REC 19H, EXE ‐ REC 19H and SAL ‐ REC 19H were harvested for assessment of specific mitochondrial injury scores using electron‐microscopy. cTnT was undetectable in all control animals ( SAL ‐5H/ SAL ‐ REC 19H and EXE ‐ CON ). cTnT increased in all animals after ISO and exercise but the response was significantly higher ( P < 0.05) at ISO ‐5H (median [range]: 2.60 [1.76–6.18] μ g · L −1 ) than at EXE ‐ END 5H (median [range]: 0.05 [0.02–0.14] μ g · L −1 ). cTnT returned to baseline at EXE ‐ REC 19H, but had not completely recovered at ISO ‐ REC 19H (median [range]: 0.17 [0.09–1.22] μ g · L −1 ). Mitochondrial “injury scores” were significantly higher ( P < 0.05) in ISO ‐ REC 19H compared to EXE ‐ REC 19H and SAL ‐ REC 19H, with no difference between EXE ‐ REC 19H and SAL ‐ REC 19H. Mitochondria from EXE ‐ REC 19H appeared aggregated in nonlinear clusters in a small number of scans. These findings suggest that acute exercise‐induced appearance of cTnT in this animal model is only associated with reversible changes in cardiomyocyte structure.